Oxygen is both the friend and the enemy of aging wines. Oxidation is the process by which exposure to oxygen changes the chemical properties of some wine components. This smooths flavors over time, resulting in the decidedly un-grapelike flavors of older wines, especially red wines. Oxygen reacts with flavor components and also with alcohol, which can result in vinegary flavors if too much oxygen is permitted.

Red wines are made from red or purple skinned grapes, and the color is partially determined by the length of time the juice stays in contact with the skins during crushing. They are best stored at about 55 degrees and served at 60 to 65 degrees F. Red wines tend to benefit from aging, becoming smoother and mellower with time. Popular red varieties include Merlot, Cabernet Sauvignon, Pinot Noir, and Zinfandel.

Sediment is a gritty substance that can form in the bottom of bottles that are aged for a long time, usually red wines. It is created when tannins undergo polymerization, binding together in long chains that then settle out as sediment. Decant wine to keep sediment out of your glass.

A small bottle of wine, holding (usually) 0.5 liters of wine. May not fit into all racking systems.

The usual size for wine bottles, 750 mL, or 3/4 of a liter. These may be Bordeaux, Burgundy or Champagne shaped bottles (or more unusual shapes).

Tannins are a phenolic compound and very important for wine aging.. Tannins create the astringent flavors in reds--the dry, bitter flavors. Wines high in tannins go well with red meat and high protein dishes, because tannins like to bind to proteins. As wines age, the tannins polymerize, binding together in long chains. The chains become sediment in the bottom of the bottle, and the flavor of the wine becomes more smooth and mellow due to the lower tannin content. Tannins also bind to other aromatic compounds in the wine, preventing those flavors from evaporating. Oak barrel aging increases the levels of tannins.

Wine ages best in cool temperatures--approximately 55 degrees F. A temperature of 55° is the perfect environment for the chemical reactions that result in good wine. But it's too cold to allow other, undesirable reactions that can give a wine unwanted aromas. Even a short exposure to extreme temperatures can trigger unwanted reactions and ruin the wine. Wine ages best at a temperature that is both cool and constant. Choosing the correct wine cellar cooling system or wine cabinet for your storage location will ensure proper temperatures for your collection.

A French term related to "terre"--land--that denotes the particular characteristics imparted by specific geographical regions due to differences in farming practices, soil quality (aeration, mineral content, water availability) and weather. The concept of terroir is the basis for the AOC regulations that restrict the labeling of wines like Champagne.

Used to describe the type of wine racks used in a wine cabinet. Universal racking indicates that most bottle sizes will fit, including standard Bordeaux bottles and larger, curvier Champagne bottles. Magnums and split bottles generally will not fit, unless specified.

A wine made from only (or primarily) one variety of grape rather than a blend of several varieties. Should not be applied to the types of grape (those are "varieties"), only to the wine made from a single variety of grape. Varietal wines must generally contain a minimum of 85% of a given grape variety to be named as such, and in many countries an even higher percentage is required.

Wine made from grapes that are all from a single vineyard or area in a single year (a "vintage wine"). Can also be applied to the grapes from a single year ("this vintage made particularly good wines"), or refer to the year and location of bottling ("What vintage is that?" "It's a '92.").

White wines are made from yellow or green skinned grapes, or sometimes from skinned red grapes. They tend to have lighter, crisper flavors with less tannin content than red wines. White wines are best served at 45-55 degrees F. Popular white wines include Chardonnay, Sauvignon Blanc, Riesling, Gewurztraminer, Pinot Gris and Pinot Grigio.